Radio-frequency (RF) MEMS devices built using standard complementary metal-oxide-semiconductor (CMOS) compatible fabrication processing on low resistivity silicon wafers are susceptible to high substrate losses due to the underlying low resistivity silicon. To address this issue, a metallic shield is commonly used to isolate the RF circuits from the lossy substrate under these circumstances. However, this metallic shield can increase the shunt parasitic capacitance of MEMS capacitors caused by the metal layers in the MEMS device and the interlayer dielectric between the shield and the device. This increase in parasitic capacitance motivates a desire to minimize the interconnect, feed, and flip chip/bond pad metallization of the MEMS device to thereby minimize the parasitics. Because the Q-factor of the RF device is inversely proportional to the resistance of the feed and interconnect metallization, however, the reduction in metallization can adversely affect the Q-factor of the device.
As a result, RF MEMS devices are desirable that have a reduced minimum capacitance (Cmin) and/or parasitic capacitance without correspondingly reducing the Q-factor of the device.